1. Field of the Invention
The present invention relates to a method of forming a monitor mark suitable for a micropattern and a monitoring method using the monitor mark.
2. Description of the Related Art
The miniaturization of semiconductor devices is greatly dependent on lithographic technology. Therefore, it is generally difficult to form a line-and-space pattern having a micro width exceeding a lithographic resolution limit. In view of such a problem, a method known as a double patterning technology using a spacer process has been proposed as a method of forming a micropattern exceeding the resolution limit (e.g., refer to Jpn. Pat. Appln. KOKAI Publication No. 2002-280338, and Jpn. Pat. Appln. KOKAI Publication No. 2006-303022). This technology features to firstly forms a double pitched pattern compared to the final product pattern, and to secondly reduce the pitch to half using means other than exposure.
In this technology, a dummy pattern is formed by lithography using, for example, a resist on an interconnect layer, and after the formation of an insulating film covering this dummy pattern, anisotropic etching such as RIE is carried out. Thus, a sidewall insulator remains on the sidewall of the dummy pattern, and then the dummy pattern is removed. The interconnect layer is etched using the remaining sidewall insulator as a mask, such that a micro interconnect pattern is formed.
In the pattern forming process using sidewall spacers, the pitch of interconnect lines is shifted due to a dimensional error after exposure or processing or due to an error in the thickness of a sidewall, and this results in a misalignment error. Therefore, in the pattern forming process using sidewall spacers, it is necessary to highly precisely measure and manage not only misalignment caused by an alignment error in an exposure device but also a pattern transfer displacement (pitch shift) error caused by the dimensional error, and control the process on the basis of the result of the measurement.
Although the micropattern can be formed by the above-mentioned method, a phenomenon occurs where the dimensions of the formed line-and-space patterns alternately vary due to, for example, a dimensional error in the resist patterns or variations in the etching rate of an underlying interconnect layer dependent on the shape of the sidewall insulator as a mask.
There is a need to readily measure the effect of such an error in a short time, and feed back the result of the measurement to a process in order to improve the quality of the pattern forming process using sidewall spacers. To this end, a scanning electron microscope (SEM) can be used to inspect the patterns, but measurement with the SEM generally takes much time and is therefore not suitable for the collection of information on a large number of points in a substrate.
Thus, there is a desire for the provision of a method of more easily measuring and evaluating a dimensional error attributed to a problem in the pattern forming process using sidewall spacers than in the case of using the SEM, and the provision of a monitor mark therefor and a semiconductor device manufacturing method using the monitor mark.